A next generation IP protocol (Internet Protocol Version 6, IPv6 for short) is a next generation Internet Protocol designed by the Internet Engineering Task Force (Internet Engineering Task Force, IETF for short) and is used for replacing the current IPv4 protocol to resolve a problem of insufficient address space.
In a network to which the IPv6 is applicable, a home gateway may connect user device to the network by using multiple broadband access servers (Broadband Remote Access Server, BRAS for short) and/or multiple gateway GRPS support nodes (Gateway GPRS Support Node, GGSN for short), and any BRAS or any GGSN is connected to the home gateway to constitute a link, that is, the home gateway connects the user device to the network by using multiple links.
As shown in FIG. 1, a home gateway is connected to both BRAS and GGSN, and the BRAS and the GGSN separately send an ICMPv6 packet carrying Prefix Delegation (Prefix Delegation, PD for short) to the home gateway in advance by using a sub-protocol: a router advertisement (Router Advitication, RA for short) protocol in the Internet Control Message Protocol version 6 (Internet Control Message Protocol Version 6, ICMPv6 for short), where the PD is a data frame encapsulated in the ICMPv6 packet. A frame format of the PD is shown in FIG. 2, and if a value of a Prefix Length field is 56, it indicates that 56-bit address information of a Prefix field is the first 56 bits of an IPv6 address that can be assigned by a BRAS or GGSN delegated by a network-side server and a PD carrying a first 56 bits of the IPv6 address may also identify a link between the home gateway and the BRAS or GGSN; if a value of a Prefix Length field is 64, it indicates that 64-bit address information of a Prefix field is the first 64 bits of an IPv6 address that is sent by the home gateway to user device. After the user device sends a connection request to the home gateway, the home gateway randomly selects one from multiple received PDs that carry the first 56 bits of the IPv6 address and that are sent by the BRAS or GGSN, adds, according to a preset rule, 8 bits behind 56 bits of the Prefix field of the PD carrying the first 56 bits of the IPv6 address to constitute a PD carrying first 64 bits of the IPv6 address, encapsulates the PD carrying the first 64 bits of the IPv6 address in the ICMPv6 packet, and sends the ICMPv6 packet to the user device by using the RA protocol. The user device generates a last 64 bits of the IPv6 address according to a MAC address of this equipment and an EUI-64 rule, combines 64 bits of the Prefix field of the PD carrying the first 64 bits of the IPv6 address with the last 64 bits of the IPv6 address to constitute a 128-bit IPv6 address, and accesses a network by using a link identified by a PD that carries the first 56 bits of the IPv6 address and that is included in the IPv6 address.
In the prior art, user device may be connected to a network by using multiple links, but, at a moment, can only access the network according to one IPv6 address by using a link identified by a PD that corresponds to the IPv6 address and that carries first 56 bits of the IPv6 address and cannot access the network by using the rest of the links, resulting in low utilization of network resources.